An optical transport network (OTN) includes a set of optical network elements (e.g., network devices), connected by optical fiber links, that provide transport, multiplexing, routing, management, supervision, and survivability functions for optical channels carrying optical signals. An OTN may provide transport for any digital client signal carried via any protocol that can be encapsulated in a format acceptable to the OTN. A metropolitan OTN is a geographical subset of an OTN that spans a geographical metropolitan area within an urban or suburban region, that is distinct from a core or backbone, which interconnects various metropolitan OTNs. Bandwidth requirements from end customers have increased substantially, and the resulting congestion and complexity has created a growing demand for higher bandwidth interfaces, such as interfaces provided by metropolitan OTNs. Metropolitan OTNs are inherently designed for short to medium length distances in metropolitan areas; that is, typically, within the limits of a single optical span and often less than a predetermined distance. Metropolitan OTNs are designed to provide services to a variety of customers with ranging requirements (e.g., from Digital Signal 0 (DS0) to 10 Gigabit Ethernet (10GE) services).
ITU-T G.872 defines the architecture of an OTN as including multiple layers, such as an Optical Transmission Section (OTS), an Optical Multiplex Section (OMS), and an Optical Channel (OCh). ITU-T G.709 defines the OCh layer structure and a frame format at an Optical Network Node Interface (ONNI) level. Each layer of transported information is made up of a payload and overheads. The OCh layer includes two main units (e.g., an Optical Data Unit of a particular level (k) (ODUk) and an Optical Transport Unit (OTU)), and transports payloads and associated overhead information. In particular, the purpose of the ODUk overhead is to carry information managing and monitoring an end-to-end connection crossing an OTN. The OCh layer and the ODUk layer span multiple layers, which may add to the complexity of the OTN. Furthermore, the OCh layer is an entirely optical layer, whereas the ODUk layer is not an entirely optical layer (e.g., the ODUk layer performs some electrical functions).
A link aggregation (e.g., as set forth in IEEE 802.3ad) is a computer networking term which describes using multiple links (e.g., Ethernet network cables and/or ports in parallel) as one logical port to increase the link speed beyond the limits of any one single link. Other terms used for link aggregation may include Ethernet trunking, port teaming, network interface card (NIC) bonding, link bundling, and/or a link aggregation group (LAG). A LAG will be used hereinafter to refer to link aggregation.